Carburetor



Patented Mar. 18, 1941 UNITED STATES &234346 CARBUBETOB George M. Bicknell, St. Louis, Mo., assgnor to Carter Carburetor Corporation, St.'Louis, Mo., a corporation ot Deiaware Application May 3, 1940, Serial No. %3,238

This invention relates to carburetors i'or internal combustion engines and consists, particularly, in novel means for preventing gaseous bubbles formed in the main fuel supply passage or discharge nozzle rrom traveling upwardly through the nozzle and carrying unvaporized uel into the mixture conduit. The application is a continuetion in part of copending application, Serial No. 255,674, filed February 10, 1939.

An internal combustion engine carburetor is frequently exposed to such high temperatures that the iuel gasifies in the main nozzle and passages leading thereto, !orming bubbles which, when they have reached sufllcient size, break loose from the surrounding metal and pass upwardly through the Iuel. Where the main nozzie passage extends upwardly at an angle from the Iuei metering oriflce, such bubbles rormed during operation ot'the carburetor may pass out- 20-wardiy through the main nozzle and result in uneven operation and excessive leanness, a condition known in the art as "surgingfi' After the engine has stopped, the heatthereot may rise sumciently, due to stopp g oi the Ian and water 25 circulation, to cause similar gasiflcation and boiling or *so-called "percolation,"-in the carburetor iuel passages and carrying or liquid i'uel over the edge of the main nozzle. This action may continue until the bowl has been run dry.

It has been suggested that percolation can be greatly restricted or stopped by the provision of a relatively large passage extending vertically upwardly rrom the base ot the main nozzle passage to the atmosphere and provided with a 35 valve at its outlet end arranged to open when the carburetor throttle valve is closed to release cases oollected in the upper part o! the passage. The throttle controlled valve has been found necessary in' order to prevent airirom bleeding 40 into the nozzle and to stabilize the fue] discharge !rom 'the nozzle. The valve has not proved wholiy satistactory, since it is dimcult to prevent it !rom leaking and it increases the cost of the carburetor and. moreover, such an arrangement 45 does not completely avoid surging.

`An object oi the present invention is to provide an "anti-pereolator" device which eliminates control valves, as described above.

Another object is to provide means tor reo stricting or preventing surfing in carburetors.

Another object is to provide an "anti-percolater" device which is a'dapted also to function as an anti-mirse device.

These objeets and other more detailed obiects 65 hereatter appear-ing are attained substantially by the structure illustrated in the accompanyng drawing in which Fig. 1 is a vertical sectional view e! a carburetor embodying the invention.

Fig. 2 is a detaii section, but showing a slight modification.

The carburetor shown is of the downdraft type including an air inlet horn l, choke valve 2 therein. venturis 3. mixing chamber 4 and outlet portion 5 fianged as at 8 for attachment to an associated internal combustion engine (not 10 shown). A throttle valve 1 is mounted between the mixture chamber and outlet portion. Adjacent the carburetor barrei is a bowl or reservoir 9 within' which iuel is maintained at a substantially constant level x-a: by the usual needie 15 v valve mechanism (not shown) controlled by iloat m. Fuel is supplied ;from the bowl to the barrel or mixture 'Conduit through a calibrated metering oriflce member ll, passage !2 opening into a normally submerged chamber !3, and main nozzie M extending upwardly at an angle from chamber 13 and opening into the interior of the upper, smallest venturi 3. Nozzle Il has an air hole Ha Iacing against the air stream and a fuel outlet Mb in the tip portion thereoi. Fuel for idling is supplied through passage IS extending from main fuel passage z to port l'i adjacent the edge o! the throttle when closed.

A relativelylarge passage or well IS extends more sharply upwardly !rom chamber !3 than the main nozzle, in the present case, vertically. above the normal fuel level. The upper two venturis 3 are supported from the wall ot the mixture conduit by rib structure s.

A passage !9 extends !rom well !5 above chamber a and terminates in a tube 20 having an outlet tip spaced slightly above or anterior to the outlet end oi' main nozzle Il. This tip may be slightly undercut, as shown in Fig. 1, or may extend axiallyot the mixture conduit, as in Fig. 2. 40

In operation. any gaseous bubbles Iorming in chamber !3 at the base of the main nozzle tend to take the easiest path upwardly, which is through well !5 instead of through the sloping, relatively small main nozzle.

The relative positioning and angular disposition oi the outlet opening o! the main nozzle and tube z are adjusted to insure, as near-ly as possible, a balanced condition in the top of the well so that tube 20 will not function as an air bleed or a mere duplicate iuel nozzle. The well must be exposed to substantially greater suction than the main nozzle before Iuel will be raised through tube 20 which extends higher than the nozzle. Thua there is little or no tendency of either liquid tuel or air being drawn in either direction through tube 20- during operation, but if !uel should pass through tube :i at high suctions, the total discharge would not be aflected. substantially, since both the tube and the main nozzle communicate with the i'uel reservoir only through restriction ii, which meters the liquid iuelv delivered to the carburetor. The outlet opening oi tube 20' should i'ace in a direction making an angle of 90 or less with the direction of air flow toprevent air bleeding therethrough into the main nozzle during operation. In Fig; 1, this angle is less than 90% the tube being undercut, and inFig. 2 the angle is 90.

Well IE is large enough to permit the release of bubbies tormed therein and in chamber i: without substantially raising the level of mel in the chamber. Gases collected in the top of chanber !5 may pass out through passage ll into the mixture conduit. but there is little or no possibllity of liquid or unvaporizeol mel being carried through this passage. Tube 20 also forms a -shield for the main nozzle which has a tendency to increase the suction applied thereto. An advantage'oi' this arrangement lies in its tendency to increase. the 'uel drawn from the main nozzle at periods 'oi low suction when the throttle valve is substantinly opened. Any function which the "anti-percoation" and "antisurge" passage exerts upon the proportioning of the mixture during normal operation may be controlled, as desired, by means of meteri orifices, bleeds. and other caliloration eents well known, and by varying the pontioning and shaping oi tube 28, without loss oi' the primar-y function of this passage:

various features of the carburetor shown are 'not essential and these may be modified as will occur to those skilled in the art without departing from the spirit of the invention. The exclusive use of all modifications as come within the scope of the appended claims is contempiated.

I claim:

1. In a downdrat carburetor, a mixture conduit including a venturi. a 'uel reservoir, a chamber adiacent the wall oi' said conduit and normally submerged in said reservoir and oo cating therewith, a main uel nozzle cating with said reservoir through a meter-ing re-' striction and extending from said chamher upwardly at an angle and discharging substantiaily at the throat of said venturi, and e pa ese ex tending from said chamber posterior to said restriction more sharply upwardly than said nozale and having an opening slightiy anterior to and in line'with the t'ozzle opening, said passage being of ample size ior releasing bubbles rrom said chamber.

2. In a downdraft carburetor, a mixture conduit including a venturi. a constant level fuel res- 5 efivoir. a main mel nozzle communicating with said reservoir through a metering restriction and 'having a portion posterior to said restriction extending upwardy at an angle i'rom below the fuel i level, said nozzle havingan opening discharging m substantially at the throatoi said-ventu'ri, and a passage extendin'g !rom the lower part ot said nozzle portion posterior to--said restriction more sharply upwardly than said nozzle portion to above the tuel level and thence into said mixture 1 conduit, said passage being or ample size tor releasing bubbles from said nozzle portion and having an opening immediately adjacent the mouth of said venturi and facing transversely of said conduit so as to 'prevent bleeding oi air into said 20 passage during operation..

i 3. In a carburetor. a downdraft mixture conduit including a venturi, a. main iuel nozzle having a metering restriction and a portion posterior to said restriction extending upwardly at an 25 angle into said Conduit and discharging into'the throat of said venturi, and an unrestricted bubble releasing passage extending from the lower part oi' said nozzle portion posterior to said restriction more sharply upwardly and to a higher level than said nozzle, said, passage having an opening positioned immediately .adjacent to and in line with the mouth of said venturi and facing in a direction making an angle oi oiless with the direction oi' air flow through said conduit so as to prevent air bleeding into said passage dur ing operation.

4. In a carburetor. e, harrel forming a downdraft mixture conduit including a venturi 'and a portion oi greater cross section, a constant level iuel reservoir, a main iuel nozzle communicating with said reservoir through a metering restriction and having an upwardly inclined part with an opening into said'venturi, and a bubble reieasing passage extenoling from said nozzle posterior to said restriction and below the iuel level more sharply upwardly and to e. higher level than said nozzle, said passage having an opening into seid larger portion' of said barrel immediately anterior to`and directly in line with said nozzle ,50 opening and said passage opening racing in a direction making an angie oi 90 or less with the normal direction oi ai'fiow through said barrel.

enonen M. BICKNELL. 55 

